Key-peck Responding Research Articles

Superstitious responding and reinforcement rate under concurrent variable-interval extinction schedules

To examine superstitious responding, four pigeons key pecked under multiple concurrent variable-interval 45 s variable-interval 90 s concurrent variable-interval 90 s variable-interval 180 s schedules in the absence of a changeover delay. The two variable-interval 90 s schedules then were replaced by extinction, and key-peck responding during extinction was examined as a function of the prevailing reinforcement rate. During the first several sessions, extinction-key responding was maintained closer to baseline levels in the presence of the higher reinforcement rate, and this effect dissipated or even reversed with continued exposure to extinction. Although extinction-key responding generally decreased to near-zero levels after several sessions, in a few instances, it continued for 30 and 45 sessions. These results demonstrate how concurrent variable-interval extinction schedules can be used to investigate what often has been labeled superstitious responding.

Further Investigation of Responding Elicited by BC and C after A+, AB-, ABC+ Training

Two experiments with pigeons explored conditioned keypeck responding to new visual targets after visual compound discrimination training. In the first experiment, pigeons were trained with an A+, AB−, ABC+, AD−, ADC+ task, in which stimulus A signalled food, stimulus compounds AB and AD signalled no food, and stimulus compounds ABC and ADC signalled food. According to both an elemental model (Rescorla & Wagner, 1972) and a configural model (Pearce, 1987) of Pavlovian conditioning, test compounds BC and DC should elicit less responding than should C alone. However, the birds responded more to BC and DC than to C. In the second experiment, another set of pigeons was trained with an A+, AB−, ABC+, AD−, ADE+ task, in which stimulus A signalled food, stimulus compounds AB and AD signalled no food, and stimulus compounds ABC and ADE signalled food. Contrary to the prediction of the Rescorla-Wagner model, keypeck responding was not less on BC and DE trials than on C and E trials in testing. However, B and D attenuated responding to E and C, respectively, when presented in compounds BE and DC. The Pearce model was able to accommodate these results.

Olanzapine, an atypical antipsychotic, increases rates of punished responding in pigeons

The effects of olanzapine [LY 170053; 2-methyl-4-(4-methyl-1-piperazinyl)-10H-thieno[2, 3b] [1,5]benzodiazepine), a potential atypical antipsychotic, were determined in pigeons whose keypeck responding was punished. These effects were compared to the anxiolytic agents chlordiazepoxide and pentobarbital, and to other antipsychotic agents. Keypeck behavior was maintained under a multiple FR30 FR30 schedule, signalled by white and red stimulus lights, respectively. Each component of the schedule alternated every 3 min with a 30-s timeout. During the white keylight component, responding was maintained by food presentation. During the red keylight component, responding was maintained by food and simultaneously suppressed by electric shock presentation, with response rates being only about 5% of those during the white stimulus light. Olanzapine (0.01-1.0 mg/kg) increased punished responding at doses below those which had an effect on unpunished responding. Clozapine (0.01-1.0 mg/kg), ritanserin (0.1-3.0 mg/kg), and, to a lesser extent, risperidone (0.1-1.0 mg/kg) were also effective at increasing punished responding. Generally, the maximum effect seen with olanzapine was equal to that seen with ritanserin, and it exceeded that seen with clozapine. However, these effects were generally less than those seen with chlordiazepoxide and pentobarbital. Haloperidol (0.01-0.1 mg/kg) was completely without effect on punished responding, while it caused decreases in unpunished behavior. These results provide further evidence that olanzapine has a profile in behavioral tests unlike the typical antipsychotic haloperidol. Moreover, this profile is similar to clozapine, a clinically effective antipsychotic with an atypical profile.

Separate and combined effects of dopamine D 1 and D 2 receptor agonists on key pecking in the developing chick

The separate and combined effects of dopamine D 1 and D 2 agonists on key-peck responding of young chicks for heat reinforcement were determined. In the first experiment, 1- and 4-day-old chicks ( n = 96) were injected SC with either distilled water or 5 mg/kg reserpine 18 h before testing. Twenty minutes before a 24-trial autoshaping session, chicks were injected IP with either distilled water or 10 mg/kg SKF 38393 and 2 mg/kg quinpirole. Chicks receiving both dopamine agonists had enhanced key-peck responding in both pretreatment conditions. In Experiment 2, and 1- and 4-day-old chicks ( n = 192) of two strains recieved 5 mg/kg reserpine SC 18 h before testing. Twenty minutes before their autoshaping session these chicks were injected IP with either distilled water, 10 mg/kg SKF 38393, 2 mg/kg quinpirole, or 10 mg/kg SKF 38393 and 2 mg/kg quinpirole. After reserpine pretreatment, chicks of both strains responded on more trials when given both dopamine agonists compared with controls given either distilled water or single agonist treatment. No age or strain differences in key pecking were produced by the combined administration of these dopamine agonists. Therefore, functional coupling of the dopamine D 1 and D 2 receptors is found within 1 day after hatching in the domestic chick.

Anticonflict and discriminative stimulus effects in the pigeon of a new methoxy-chroman 5-HT1A agonist, (+)S 20244 and its enantiomers (+)S 20499 and (−)S 20500

The present experiments examined the behavioral and receptor binding characteristics of new 5-HT1A methoxy-chroman derivatives in procedures known to be sensitive to the activity of 5-HT1A compounds. Key peck responding of pigeons was maintained by a 30-response fixed-ratio schedule of food delivery. In studies involving punished responding, every 30th response during one keylight stimulus also produced shock ("conflict" procedure). In drug discrimination studies, pigeons were trained to discriminate injections of the 5-HT1A agonist 8-OH-DPAT (0.3 mg/kg) from saline. Three forms of the methoxy-chroman compounds were tested: the enantiomers (+)S 20499 (0.01-3.0 mg/kg) and (-) S 20500 (0.3-5.6 mg/kg), as well as the racemic mixture (+)S 20244 (0.03-5.6 mg/kg). (+)S 20499 was approximately 10-fold more potent than (-)S 20500 in producing maximal increases in punished responding. (+)S 20244 was comparable in potency to (-)S 20500 in producing maximal increases in punished responding, but increases also occurred at much lower doses with (+)S 20244 and the magnitude of the effect with (-)S 20500 was less than that of the two other compounds. While increases in punished responding were observed with all three drugs at doses that did not affect unpunished responding, the highest doses of all drugs decreased unpunished responding. All compounds substituted for 8-OH-DPAT in the drug discrimination procedure, suggestive of 5-HT1A agonist activity. (+)S 20499 was approximately 30-fold more potent than (-)S 20500 in substituting for 8-OH-DPAT and 3-fold more potent than the racemate. All three compounds bound with high affinity to pigeon cerebrum receptor sites labelled by [3H]8-OH-DPAT. As in behavioral studies, (+)S 20499 was approximately 10-fold more potent than (-)S 20500 in displacing [3H]8-OH-DPAT (IC50 = 2.79 versus 20.3 nM). These studies demonstrate that the enantiomers of this compound, as well as the racemic mixture, are effective 5-HT1A compounds and that (+)S 20499 in particular is likely to be a clinically effective anxiolytic and/or antidepressant.

Shock postponement reverses the effects of cocaine on the punished pecking of pigeons

The effects of cocaine on punished and unpunished key peck responding of pigeons was examined before and after a history of treadle pressing maintained by shock postponement. In one schedule component, the first peck after 3 min produced grain. The alternate component was similar, but every 30 responses was also punished by a mild shock. Punished responding occurred at approximately 25% of the rate of unpunished responding. Cocaine (0.1–10.0 mg/kg IM) did not affect or decrease punished responding; unpublished responding was not systematically affected. Next, a foot treadle was installed and treadle presses postponed shocks for 25 s; shocks occurred every 5 s in the absence of pressing. The treadle was removed when shocks were reliably postponed. Next, the multiple schedule of key pecking was reinstated. At least one dose of cocaine now increased punished pecking; unpunished responding was not systematically altered. These results complement related findings with monkeys and show that pigeons are suitable subjects for studying the reversal of the effects of cocaine on punished responding by a history of postponing shock.

Economic variables affecting punishment warmup

Keypeck responding of a pigeon was maintained by a variable-interval (VI) 3-min schedule of positive reinforcement and punished according to a VI 30-sec schedule of electric shock presentations. During the short-session conditions, sessions lasted approximately 1 h and the subject was postfed immediately after the session. During the long-session condition, sessions lasted approximately 3 h and the subject was postfed approximately 12 h after the session. The short-session conditions consistently produced periods of low-rate responding, with a gradual increase in response rates at the beginning of the sessions. The long-session condition attenuated this warmup period. During the different conditions, the subject’s behavior produced different proportions of the subject’s total food intake. These results, therefore, may reflect the influence of economic context on response strength and the resulting effectiveness of a particular set of punishment parameters.

Dopamine antagonists produce an age‐dependent increase in the responding of the young chick

In three experiments the effects of dopamine receptor antagonists on response-contingent punishment and autoshape learning of 1- and 4-day-old chicks were determined. In the first two experiments, 1- or 4-day-old chicks (N = 120) were trained to key-peck for heat reward and then injected intraperitoneally (ip) with either haloperidol (1.5, 2.5, or 5.0 mg/kg) or saline (Experiment 1) and with either haloperidol (2.0 mg/kg), sulpiride (50 mg/kg) or saline (Experiment 2) 30 min before a 96-trial response-contingent punishment session. In Experiment 3, 1- and 4-day-old chicks (N = 48) were injected ip with saline or haloperidol (2.0 mg/kg) 30 min prior to a 30-trial autoshape learning session. In both the punishment and appetitive tasks 1-day-old chicks pretreated with either haloperidol (1.5 to 2.5 mg/kg) or sulpiride showed a significant increase in key-peck responding compared with their saline injected controls. In contrast, 4-day-old chicks given either haloperidol (2.0 mg/kg) or sulpiride did not differ significantly from saline treated chicks on the punishment task, and on the autoshape task haloperidol-treated 4-day-old chicks responded on fewer trials than did their saline controls. These results indicate that dopaminergic synaptic transmission in the young chick as measured by dopamine D2 receptor blockers is functionally different at 1 compared with 4 days of age.

EFFECTS OF ALTERNATIVE REINFORCEMENT SOURCES: A REEVALUATION

The effects of two alternative sources of food delivery on the key-peck responding of pigeons were examined. Pecking was maintained by a variable-interval 3-min schedule. In the presence of this schedule in different conditions, either a variable-time 3-min schedule delivering food independently of responding or an equivalent schedule that required a minimum 2-s pause between a key peck and food delivery (a differential-reinforcement-of-other-behavior schedule) was added. The differential-reinforcement-of-other-behavior schedule reduced response rates more than did the variable-time schedule in most instances. The delay between a key peck and the next reinforcer consistently was longer under the differential-reinforcement-of-other-behavior schedule than under the variable-time schedule. Response rates and median delay between responses and reinforcers were negatively correlated. These results contradict earlier conclusions about the behavioral effects of alternative reinforcement. They suggest that an interpretation in terms of response-reinforcer contiguity is consistent with the data.

Effects of buspirone differ from those of gepirone and 8-hydroxy-2-(di-n-propylamino)tetralin (8-OH-DPAT) on unpunished responding of pigeons

Under several behavioral procedures, such as punished responding and drug discrimination, the effects of the atypical anxiolytic buspirone are similar to those of its analogue gepirone, and to those of the 5-HT1A receptor agonist 8-OH-DPAT. Similarities in the effects of these compounds occur despite the fact that buspirone produces strong dopaminergic actions, whereas both gepirone and 8-OH-DPAT effects mainly appear to be serotonergically mediated. When keypeck responding of pigeons was maintained under a multiple 3-min fixed-interval, 30-response fixed ratio schedule of food presentation, responding under both the fixed-interval and fixed-ratio schedules was decreased over a range of buspirone doses (0.3–5.6 mg/kg). As has been reported with many antipsychotic compounds, performance under the fixed-interval schedule was more sensitive to the rate-decreasing effects of buspirone. In contrast, both gepirone (0.03–3.0 mg/kg) and 8-OH-DPAT (0.03–1.0 mg/kg) increased responding under the two schedules. Differences in the effects of buspirone from the other compounds in this study, compared to the similar effects of these drugs obtained using other procedures, emphasize the importance of the specific behavior as a determinant of drug action. The multiple fixed-interval, fixed-ratio schedule may be useful for delineating the relative balance of dopaminergic and serotonergic effects produced by drugs that are less apparent using other behavioral procedures. Additionally, since the effects of these substances under the multiple fixed-interval, fixed-ratio schedule closely parallel the different neurochemical changes produced by these drugs, further analyses of other novel anxiolytic drugs under this procedure will complement the study of these compounds using other methods and should aid in the eventual clarification of the behavioral and neurochemical actions of this class of drugs.

CHANGES IN FUNCTIONAL RESPONSE UNITS WITH BRIEFLY DELAYED REINFORCEMENT

In two experiments, key-peck responding of pigeons was compared under variable-interval schedules that arranged immediate reinforcement and ones that arranged unsignaled delays of reinforcement. Responses during the nominal unsignaled delay periods had no effect on the reinforcer presentations. In Experiment 1, the unsignaled delays were studied using variable-interval schedules as baselines. Relative to the immediate reinforcement condition, 0.5-s unsignaled delays decreased the duration of the reinforced interresponse times and increased the overall frequency of short (<0.5-s) interresponse times. Longer, 5.0-s unsignaled delays increased the duration of the reinforced interresponse times and decreased the overall frequency of the short interresponse times. In Experiment 2, similar effects to those of Experiment 1 were obtained when the 0.5-s unsignaled delays were imposed upon a baseline schedule that explicitly arranged reinforcement of short interresponse times and therefore already generated a large number of short interresponse times. The results support earlier suggestions that the unsignaled 0.5-s delays change the functional response unit from a single key peck to a multiple key-peck unit. These findings are discussed in terms of the mechanisms by which contingencies control response structure in the absence of specific structural requirements.

A ROLE FOR NEGATIVE REINFORCEMENT OF RESPONSE OMISSION IN PUNISHMENT?

This experiment attempted to disentangle response-rate reductions controlled by the direct suppressive effects of a punisher from those due to negative reinforcement of response omission. Key-peck responding of pigeons was maintained by a conjoint variable-interval 3-min schedule of food presentation variable-interval 30-s schedule of response-dependent electric shock presentation. Omission of responses for 5, 10, or 30 s resulted in the possibility of canceling a scheduled shock. Response rates were a function of required pause duration, with lower rates occurring when longer periods of response omission were required for shock cancellation. These results show that, with several parameters of punishment held constant, response rates were controlled by the negative reinforcement contingency. Such a finding argues for renewed consideration of the role of negative reinforcement in punishment contingencies.

HOMOGENEOUS CHAINS, HETEROGENEOUS CHAINS, AND DELAY OF REINFORCEMENT

Three pigeons responded on two-component chain schedules in which the required response topography in the initial and terminal links was similar (a homogeneous chain) or dissimilar (a heterogeneous chain). Key-peck responding in the initial link under a variable-interval 60-second (VI 60) schedule produced a terminal link in which, in different conditions, either key pecking or foot treadling was reinforced according to a VI 60 schedule. Multiple VI 60 VI 60 schedules, in which the responses required in the chain schedules were maintained by primary reinforcement in the two components, preceded and followed each type of chain. These multiple schedules were used to ensure that both responses occurred reliably prior to introducing the chain schedule. Key-peck response rates in the initial link of the chain consistently were higher during the homogeneous chain than during the heterogeneous chain. These results illustrate that intervening events during a period separating an operant response from primary reinforcement influence that operant, independently of the delay between the response and reinforcement.

BRIEFLY DELAYED REINFORCEMENT: AN INTERRESPONSE TIME ANALYSIS

Key-peck responding of pigeons was compared under VI or DRL schedules arranging immediate reinforcement and briefly (.5 sec) delayed reinforcement. Delays were either signaled by a blackout in the chamber, unsignaled, or unsignaled with an additional requirement that responding not occur during the .5 sec interval immediately preceding reinforcement (response delay). Relative to the immediate reinforcement condition, response rates increased during the unsignaled delay, decreased during the signaled delay, and were inconsistent during the response delay condition. An analysis of interresponse times (IRTs) under the different conditions revealed a substantial increase in the frequency of short (0 to .5 sec) IRTs during the unsignaled condition and generally during the response delay conditions compared to that during the immediate reinforcement baseline. Signaled delays decreased the frequency of short (0 to .5 sec) IRTs relative to the immediate reinforcement condition. The results suggest that brief unsignaled delays and, in many instances, response delays increase the frequency of short IRTs by eliminating constraints on responding.

DEPENDENCY, TEMPORAL CONTIGUITY, AND RESPONSE‐INDEPENDENT REINFORCEMENT

A comparison was made of the effects of variable-interval, variable-time, and tandem variable-interval fixed-time schedules on key-peck responding of pigeons. The variable-interval component of the tandem schedule retained the response-reinforcement dependency; the fixed-time component allowed the temporal proximity between responding and reinforcement to vary, constrained only by the duration of the fixed-time interval. Response rates were highest during the variable-interval and lowest during the variable-time schedule. Intermediate response rates occurred during the tandem schedule. The results of a yoked control condition showed that the effects of the tandem schedule were not due simply to changes in reinforcement distribution or frequency. The results suggest that substantial reductions in responding occur when reinforcement is response-dependent but not necessarily contiguous with the response required to produce reinforcement.

BEHAVIORAL CONTRAST AS A FUNCTION OF THE DURATION OF AN IMMEDIATELY PRECEDING PERIOD OF EXTINCTION1

For four pigeons key-peck responding was reinforced on a variable-interval reinforcement schedule in the presence of a vertical white line. When response rates had stabilized a horizontal white line was introduced, in the presence of which reinforcement was not available (extinction). The horizontal line was presented once per session, immediately before the vertical line was presented. The duration of the horizontal line varied randomly from session to session, being either 0 sec (i.e., no presentation), 10 sec, 30 sec, 2 min, 10 min, 40 min, or 120 min. When the horizontal line was present for more than 0 sec, behavioral contrast was obtained in the presence of the following vertical line. Contrast increased with increasing durations of the horizontal line, asymptoting when the horizontal line was present for 40 min.